Chemistry The Periodic Table Part IV: Iron, Zinc, Selenium

The periodic table organizes elements by an atomic number, based on the amount of protons in each element's nucleus. Other factors include electron configuration and recurring chemical properties. Elements are listed in order of increasing atomic number along with its chemical symbol in each box. The elements iron, zinc and selenium help promote health and fight disease and have commercial uses. Iron zinc and selenium, which happen to exist naturally, are also referred to as trace minerals because humans need only small amounts of them.